Shriveling Cactuses

Cactuses come in many shapes and sizes, but suffer similar problems.

Plants in the family Cactaceae, collectively known as cactus, are no-fuss plants kept in homes and offices. Some of these succulent, spiny plants are hardy enough to be planted outside in U.S. Department of Agriculture plant hardiness zones 3b through 11, depending on the species. One of the most common problems for cactus-keepers is the shriveling of their charges -- this symptom can be the result of a variety of problems, many of which are simple to correct.

Water

Cactuses have a reputation for withstanding extreme drought and requiring little to no water -- this myth leads to disappointment for new cactus growers. Some cactus species may require as much water as green flowering annuals during their active growing season. Because cactuses can't tolerate standing water or constantly wet roots, they are planted in loose, fast-draining soils that have poor water retention. When a cactus begins to shrivel, first try giving it a long, tall drink -- never water a cactus shallowly. If it doesn't perk up in a few days, it's time to explore other issues.

Root Problems

Cactuses in pots can become so root bound they are unable to take up water and nutrients efficiently, causing them to slowly shrivel. If your plant doesn't respond to a good watering, removing it from the pot and checking the root system may reveal the source of your problem. Root-bound plants have white, healthy roots that have grown into a tangled mass. You'll need to do careful root pruning and separation to save these plants. If the roots are brown, black, smell bad or are otherwise soft, your plants may be suffering from one of many root rots brought on by chronic over-watering.

Environmental Impact

Even though they are generally hardy, cactuses cannot tolerate dramatic changes in their environment. If your cactus sits in a window, it may shrivel after experiencing damage from excessive sunburn or freeze from direct contact with the glass. You may not notice these damaged spots for months if you water the cactus where it lives and rarely move it. Keep your indoor cactus in a draft-free spot away from heating and air-conditioning vents and sunlight filtered through glass, because this can intensify the effects of ultraviolet rays.

Disease

Many fungal diseases of cactuses result in oozing, soft sores on their surfaces, but sometimes, as in the case of cactus stem rot, the plants dry out instead. Fusarium wilt and crown and root rots also cause the cactus to dry out and collapse by interfering with its ability to take up water. Cactus stem rot may be treated with fungicide, if caught early, but crown and root rots are more complex problems. They are often initiated by constantly wet soils -- these conditions must be corrected first. You may be able to save your cactus if the rot isn't extensive, but it will need careful nurturing until new roots emerge. Fusarium wilt cannot be treated, unfortunately.

Pests

Scale insects, mealybugs and nematodes are common pests of cactuses, both in the garden and in the home. Nematodes attack the root systems, siphoning away both water and minerals -- a severe infestation may cause a cactus to shrivel because it is unable to bring enough water into its systems. Scales and mealybugs suck juices directly from plant tissues, but may be difficult to differentiate from structures on the cactus itself, such as fuzzy tufts, irregular bumps and other usual features on the plant. Sap-sucking insects are easy to kill on a cactus with sprays from water jets, insecticidal soaps or horticultural oils. Always test a small spot on each cactus with the chemical you intend to use a few days before you treat the whole plant.